The present invention relates to a shiftable bottom bracket gear train for a bicycle and the like, including a bottom bracket tube, a gear train housing with associated sprocket and a disk arranged in parallel as well as a drive shaft extending through the bottom bracket tube in an axial direction and a drive shaft operatively connected with pedal cranks, in which a shift axle is arranged which is connected with a coupling piece and can be controlled from the outside with a shifting member.
A shiftable bottom bracket gear train of the aforedescribed type which operates according to the principle of a planetary gear is disclosed in the published patent application EP 0 562 470 A1. Characteristic for such gear trains is that they have only a single input and a single output which are coaxially arranged. Because these gear trains also change the output torque, a part of the gear train must be retained as torque support. In the conventional bottom bracket, the torque support is provided by a torque lock which includes a lever arm that is attached on the rear wall of the gear train housing or is integrated in the housing, wherein the lever arm is fixedly connected with the rear-wheel fork. With this torque lock, a torque is supported which acts essentially on the rear wall of the gear train housing. With this arrangement, the frame must disadvantageously have a certain shape to enable attachment of the torque lock on the rear-wheel fork.